Supersonic airflow over components such as the internal portion of aircraft engine inlets and aircraft airfoils, can generate shock waves. These shock waves oscillate back and forth and causes the air flow to separate from the surface within engine inlets or on airfoils. Flow separation on airfoils can result in loss of lift and can ultimately cause a stall. Further, these shock waves can cause increased drag and buffeting of control surfaces attached to the trailing edge of the wing. Similar separation conditions can also occur at engine inlets, and other areas of the aircraft.
One approach to preventing or attenuating flow separation is through the introduction of vortices in the boundary layer or sub-boundary layer region. Vortex generators that project from the surface of the engine inlet or airfoil in supersonic airflow applications can thus be utilized to prevent or attenuate flow separation. The vortex generators proposed previously for supersonic engine inlets primarily consist of a plurality of short (smaller than the boundary layer height), thin rectangular blades (or microvanes) located downstream of the leading edge of the engine inlet and upstream of the point on the surface within the engine inlet where flow separation would occur without the vortex generator.
In a typical supersonic application, the blades are generally aligned with the path of air or at an acute angle with respect to the line of flight. Vortices that form off the tips of the blades can draw air down from the upper region of the boundary layer down toward the near-wall region to attenuate flow separation and reduce unwanted aerodynamic phenomena associated with flow separation, such as drag, aerodynamic blockage, and shock dithering. However, rectangular vortex generators are deficient for practical applications when considering needs for reliability, maintainability, and survivability particularly in engine inlets. Thin, rectangular vortex generators lack the robustness to survive the harsh pressure and aerodynamic loads, and heat erosion. The thin, rectangular vortex generators also do not tolerate damage due to debris that may impact the vortex generator. Furthermore, rectangular microvanes have been historically difficult to incorporate into a producible manufacturing process.
While current state-of-the-art vortex generator designs and integration approaches are feasible for attenuating flow separation in supersonic applications, an improved solution would be desirable to increase the robustness of vortex generators.